1. Field of the Invention
The present invention relates to a communication apparatus which responds to a plurality of different call signals supplied thereto via a single communication line or channel.
2. Related Art Statement
A call signal is used when one of a plurality of communication apparatuses calls another of the communication apparatuses. For example, in the case where a first telephone set requests an exchange of a telephone company to call a second telephone set, the exchange supplies a call signal to the second telephone set to place the second telephone set in an operational state thereof in which a user of the second telephone set can talk with a user of the first telephone set. More specifically, the second telephone set produces a calling sound in response to the call signal supplied thereto, so that when the user of the second telephone set picks up a handset, he or she can talk with the user of the first telephone set.
In the case where a single communication apparatus is used with a single communication line, for example, a single telephone set is used with a single telephone line, the exchange of the telephone company supplies a single sort of call signal. However, in the case where a plurality of communication apparatuses are used with a single communication line, for example, a telephone set and a facsimile machine are used with a single telephone line, the exchange of the telephone company is required to supply different sorts of call signals to the telephone set and the facsimile machine, respectively, via the single telephone line.
Different sorts of call signals are also needed in the case where wire communication is carried out between or among two or more communication apparatuses which are connected with each other such that they are always communicatable with each other, or in the case where wireless communication is carried out between or among two or more wireless communication apparatuses.
There is known a telephone company which offers the service of allotting a plurality of different call numbers to a single communication line according to a common numbering rule employed by the company.
Subscribers of the telephone company can enjoy this service by using a facsimile machine or a telephone set in relation with each of the different own call numbers. In this case, a greater number of facsimile machines or telephone sets may be used with a smaller number of communication lines. Otherwise, the subscribers can enjoy the service by using a telephone and facsimile (T/F) apparatus which possesses both the telephone and facsimile functions and has means for automatically switching the T/F apparatus between those two functions. In the latter case, one of the different own call numbers may exclusively be used in relation with the facsimile function and another of the own call numbers, or the other own call number, may exclusively be used in relation with the telephone function. An example of the T/F apparatus is disclosed in Japanese Patent Application laid open under Publication No. 4-48855.
The identification of each one of the different call numbers allotted to the single communication line, from the other call numbers, is carried out by supplying, to the communication line, different call signals corresponding to the different call numbers, respectively. For example, a basic call signal and a modified call signal obtained by adding a different signal to the basic call signal may be employed to this end. Otherwise, different call signals having different signal patterns may be used.
There is known the "distinctive ringing" service or "dial-in" service wherein different call numbers are identified by different call signals having different signal patterns, respectively. In the distinctive ringing service, the signal pattern of each call signal supplied via a single communication line to a facsimile machine is directly utilized by the called facsimile machine to ring, i.e., produce a calling sound. That is, the ringing device of the called facsimile machine produces a calling sound having a sound pattern corresponding to the signal pattern of the call signal supplied thereto. Thus, different calling sounds having different sound patterns are produced by a single facsimile machine in response to different call signals, respectively. The user of the facsimile machine can identify which call number is being used to call the facsimile machine, by hearing the sound pattern of the calling sound being produced by the ringing device. Owing to the distinctive ringing service, the user can easily judge whether his or her necessary information is being received by the facsimile machine.
Even though different call signals are supplied to call a single facsimile machine in relation with different call numbers allotted thereto and different calling sounds having different sound patterns are produced by the facsimile machine according to the different signal patterns of the call signals, each of various proper functions of the facsimile machine responds in the only and same manner, irrespective of whichever call number is being used to call the facsimile machine. For example, the facsimile machine transmits the only and same transmitter-identifying information to a calling facsimile machine, whichever call number may be used by the calling facsimile machine. In those events, therefore, the facsimile machine functions as if the machine had the only and same call number in spite of actually having two or more own call numbers allotted thereto by the telephone company. Thus, the user cannot effectively utilize the different own call numbers given to the facsimile machine.
U.S. Pat. No. 5,200,992 discloses a facsimile machine which has an outside-line call number allotted thereto according to a first or "public" numbering rule employed by a telephone company, and an extension-line call number allotted thereto according to a second or "private" numbering rule employed by the user of that facsimile machine and other facsimile machines to which the first facsimile machine in question is connected via the extension lines. When the facsimile machine is called using the outside-line call number by an outside facsimile machine, the called machine sends back or transmits the outside-line call number to the calling machine so as to inform that the called machine is receiving image information from the calling machine. Similarly, when the facsimile machine is called using the extension-line call number by another facsimile machine of the user, the called machine transmits the extension-line call number to the calling machine for the same purpose.
However, the above-identified facsimile machine cannot function as if the machine had two or more outside-line call numbers, or two or more extension-line call numbers. When the prior machine is called through the outside lines, the only and same outside-line call number can be used to call the machine. Similarly, when the prior machine is called through the extension lines, the only and same extension-line call number can be used to call the machine.